Early movers: UAL, DIS, WFM, YELP, SDRL, WDC & more

United Continental — CEO Oscar Munoz said in an email to employees that the company "followed established procedures" when it removed a passenger from an overbooked flight. Munoz added the removed passenger was being "disruptive and belligerent." The company's stock slipped more than 2 percent in the premarket.

Qualcomm — The chipmaker is countersuing Apple in a dispute over mobile technology licensing fees. The countersuit comes about three months after the iPhone maker said Qualcomm has been charging royalties for "technologies they have nothing to do with."

Yelp —Analysts at Pacific Crest upgraded Yelp's stock to overweight from sector weight and set a price target of $43, representing a 31.3 percent potential upside. "We believe competitive concerns over YELP's relevance are overdone, while self-serve's ease and utility are underappreciated," Pacific Crest said in a note.

Western Digital — The firm's stock rose more than 2 percent in the premarket after analysts at JPMorgan upgraded the stock to "overweight" from "neutral," and raised their price target to $116 from $80. JPMorgan also said Western Digital still has "significant potential" to reduce costs once synergies from the HGST and Sandisk acquisitions are realized.